1. Field of the Invention
The present invention relates to a molded surface fastener made of thermoplastic synthetic resin material and having engaging elements molded integrally with a surface of a flat substrate and independently of each other, and specifically, to a molded surface fastener which can be molded in various sizes, ranging from a fine size to a normal size, which is suitable for various usage in many fields, and which can be molded continuously and efficiently through a single step by using a simple apparatus. This invention also relates to a molding method and a molding apparatus of the same molded surface fastener.
2. Description of the Related Art
Conventional molded surface fastener is produced by various methods. A typical example is a method for producing a surface fastener by complete batch process by injection molding. Another typical method is a process for molding engaging elements successively and integrally with a flat substrate by rotating in one direction a die wheel having on its peripheral face a large number of cavities for molding the engaging elements and continuously introducing molten resin material into the peripheral face of the die wheel. By these methods, various conventionally and widely known shapes of engaging elements such as a palm shape and a hook shape can be molded.
Furthermore, another know method employs an extrusion die in which a large number of substantially T-shaped extruding openings are arranged side by side and have lower ends communicating with each other. By extruding molten resin simultaneously through the extruding openings, a plurality of ribs which are substantially T-shaped in section are successively molded on a surface of a flat substrate. Then, the molten resin molded material is hardened by cooling. Thereafter, the ribs are successively cut in a perpendicular direction or in a direction with an appropriate inclination angle with respect to a horizontal plane where the ribs are arranged such that each of the cut ribs have a predetermined thickness. At this time, the flat substrate is left uncut. After the cutting process, the flat substrate is drawn in a direction of molding, until the cut engaging elements are separated from each other with a desired pitch, thereby producing the molded surface fastener.
According to the above molding methods, the shape or the size of the engaging elements is limited, if their productivity is high, while a continuous molding is difficult to achieve or a number of processes increases so that the productivity is decreased, if the shape or the size of the engaging elements is optional to some extent. Both the cases have extreme advantages and disadvantages.
Particularly, in the above process wherein the ribs of the molten resin molded material having ribs extruded from the extrusion die to the surface of the flat substrate are cut and the substrate is drawn, a sectional shape of an engaging head of each engaging element can be optical to some extent. However, three steps, i.e., an extrusion molding, cutting of ribs, and drawing are required. Specifically, a high processing accuracy is required especially to cut the ribs, so that maintenance and management for this purpose requires considerable workload and time.